1. Field of the Invention
The present invention relates to a method for determining whether a photographic image is a different-light-source photographic image and a photographic image processing apparatus.
2. Description of the Related Art
Normally, a film used for photography is referred to as “a daylight film”. If photography is performed with a solar light or a strobe light, a photograph having an appropriate color balance is obtained. However, since photography is performed in various situations, inappropriate images are, quite often, recorded on a film. Examples of photographic scenes include a scene photographed with a tungsten light, a scene photographed with a fluorescent light, a scene photographed underwater, and the like. Thus, scenes are photographed using different light sources. For example, a photographic image photographed with the tungsten light is generally yellowish and that photographed with the fluorescent light or photographed underwater is generally bluish.
As conventional methods for determining whether photographic images are photographed using different types of light sources, there are known the following techniques. Japanese Unexamined Patent Publication No. 2001-238177 discloses a technique for acquiring additional information such as a position, a climate, and a time when a subject is photographed by a camera, estimating a photographic scene based on the additional information, and performing an image processing such as a gradation processing according to the estimated photographic scene. Japanese Unexamined Patent Publication No. 2002-257627 discloses a technique for fetching two different pieces of image data on cuts in an infrared region from the same subject, and determining types of photographic light sources based on comparison between the images. Japanese Unexamined Patent Publication No. 7-219077 discloses a technique for estimating a type of a light that illuminates a subject based on average brightness information during photography and presence or absence of a flash light.
However, the conventional methods have the following disadvantages. With the method disclosed by Japanese Unexamined Patent Publication 2001-238177, it is required to additionally provide the camera with a device for inputting information on photographic scenes. The camera is, therefore, limited to a specific expensive camera. For an image photographed by an ordinarily available camera which does not include such a function, the method cannot be used. With the method disclosed by Japanese Unexamined Patent Publication 2002-257627, similarly to the method disclosed by Japanese Unexamined Patent Publication 2001-238177, it is required to provide an expensive different light source determination apparatus. With the method disclosed by Japanese Unexamined Patent Publication 7-219077, if it is erroneously determined that an image obtained by photographing a scene in which a yellow signboard is included in a subject is a photograph taken with a tungsten light, and image data is corrected based on the erroneous determination, then a color failure occurs.